There Is No Such Thing As An Invalid Unit

The Mars Climate Orbiter was a spacecraft launched in the closing years of the 1990s, whose job was to have been to study the Martian atmosphere and serve as a communications relay point for a series of other surface missions. It is famous not for its mission achieving these goals, but for the manner of its premature destruction as its orbital insertion brought it too close to the planet’s atmosphere and destroyed it.

The ill-fated Mars Climate Orbiter craft. NASA [Public domain].The cause of the spacecraft entering the atmosphere rather than orbiting the planet was found in a subsequent investigation to be a very simple one. Simplifying matters to an extent, a private contractor supplied a subsystem which delivered a reading whose units were in the imperial system, to another subsystem expecting units in the SI, or metric system. The resulting huge discrepancy caused the craft to steer towards the surface of the planet rather than the intended orbit, and caused the mission to come to a premature end. Billions of dollars lost, substantially red faces among the engineers responsible.

This unit cock-up gave metric-using engineers the world over a brief chance to feel smug, as well as if they were being honest a chance to reflect on their good fortune at it not having happened on their watch. We will all at some time or another have made an error with respect to our unit calculations, even though in most cases it’s more likely to have involved a simple loss of a factor of ten, and not with respect to a billion dollar piece of space hardware.

But it also touches on one of those fundamental divides in the world between the metric and imperial systems. It’s a divide that brings together threads of age politics, geography, nationalism, and personal choice, and though it may be somewhere angels fear to tread (we’ve seen it get quite heated before to the tune of 885+ comments), it provides a fascinating subject for anyone with an interest in engineering culture.

The King’s Foot, And A Cube Of Water

Before we look at those threads and descend into the realm of opinion, it’s worth examining the basis of fact upon which they sit. There are three fundamentals to consider, the origins of the imperial units, those of their metric counterparts, and that when it comes to metrology there is no such thing as an invalid unit, providing that the unit in question has a consistent and valid definition.

Imperial units, at least as far as they are understood where this is being written, are the standardised version of the English system of units as defined by the British government in the 1824 Weights and Measures Act. Prior to that date they had been part of a system of customary mediaeval measurements with roots in Roman and northern European customs including it is reputed, the length of the King’s foot. But of course the astute amongst you will point out that these British units bear some differences from the similar American units. For example, 1 imperial gallon is equivalent to about 1.2 US gallons, which in turn in the metric system is about 4.54 litres. This divergence is accounted for by the two countries adopting different standardisations of the customary units in the decades following American independence.

The metric units with which we are familiar have their legal origins in post-revolutionary France, as a solution to the chaos of customary units that had been a despised feature of French commerce. They were the fruition of proposals that had come from a variety of scientists and thinkers across the European continent throughout the period of the Enlightenment, as for the first time they brought together the definition of a system of measurements not only under a consistent numerical base, but with coherent links between units. Thus a metre was a ten-millionth of the length of the meridian from the North Pole through Paris to the Equator, a volume of 1 litre could be expressed as a cube of side 0.1 metre, and a mass of 1 kilogramme was defined as that of a litre of water. From this beginning has evolved the coherent system of SI (Système international) units, in which all units can be defined in terms of a small set of base units with the same consistent numerical base. The base units may now be largely defined in terms of constants rather than the physical standards of post-revolutionary France, but the elegance and consistency of the system remains.

Reading the thumbnail descriptions of the two systems, I’m sure you will have made up your own minds which you would prefer to use. Very few of you will be sitting on the fence, and you’ll all be prepared to fight your own corners in the comments. But before going there it’s worth making what is probably the most important point on this page, that there is no such thing as an invalid unit. We may prefer to use one or the other for some extremely valid reasons, but there is no reason whatsoever why engineering achievement should be held back by our choice. Consider all the engineering achievements of the past few hundred years that were made by engineers wielding micrometer screw gauges calibrated in thousandths of an inch rather than in milimetres, did they somehow perform less well for their choice of units? The Apollo astronauts might comment that they didn’t.

Doing Time For A Pound Of Bananas

In the United Kingdom, the metric system forms the official as well as the generally accepted set of units. There are however customary exceptions to this, such as pints of milk or beer and distances measured in miles, and it is fair to say that at times it has entered the realm of politics. Metrication came within the same decade as our entry into what would become the European Union, so it was something that could easily be portrayed by politicians with a particular axe to grind as a confusing foreign system imposed from Europe. We’ve had various controversies such as the “metric martyrs”, market traders prosecuted for selling produce by the pound rather than by the kilo, and it’s an issue over which passions can still run high.

As a Brit born a year or two before European Community membership then, it’s a subject of which you might say I have had a grandstand view. As an engineer I use metric units throughout as the obvious choice, yet with formative years in a largely pre-metric era there are still customary Imperial units with which I am familiar. My car for instance has 35PSI in its tyres and does 70 miles to the gallon on a good run even though I haven’t been able to buy fuel by the gallon for nearly a quarter century, and when it comes to textiles I use inches probably because my mother did.

So if I had to choose a side of the fence upon which to sit on the question of units I guess I’ve made myself pretty clear as a metric user. One of the most enlightening series of lessons of my whole school career was that in which the SI system was explained and in which everything in the world that could be measured fell into order. Once you have had that explained to you it’s difficult to go backwards. But I understand those contractors who inadvertently sent their craft spinning into the Martian atmosphere, and realise that in another decade, it might have been me sitting in their hot seat.

You’ll all have strongly held views on the subject of units, which you’ll no doubt be anxious to share in the comments. But as I mentioned earlier, we’ve already had that discussion.

Given the story of the Mars Climate Orbiter with which we started, it would be most interesting to hear from engineers who have crossed the gap between the different sets of units. The Hackaday readership contains an astonishing breadth of experience. Please share your stories of where a project was saved at the last minute (or perhaps failed in some spectacular way) because of a mismatch in the measurement language used by different parts of the project.

Nope, in troll units:
on the scale of :
Barely-a-lol – Brian-Benchoff – Nuclear-blast
With plenty of space between….
Brian Benchoff has been added as a mid-size point for scale size indication or like what 10 Meters is to a Kilometer in scale.

I am capricious and eclectic in my use of units, I’ll typically woodwork in inches and do circuit boards in millimeters. I am also a math user and can brain the convertimation of one unit to another.

“This unit cock-up gave metric-using engineers the world over a brief chance to feel smug, as well as if they were being honest a chance to reflect on their good fortune at it not having happened on their watch.” A HaD columnist screwed up the metric unit multiplier on a piece in the last month. One could argue that Imperial is less typo prone, if you drop a character from in or ft it’s obvious and is checked, if you drop an m from mm you could be in deep doodoo.

But if you drop an m from mm (or double hit the m for mmeters), the result is probably absurd, making it obvious. Thereby providing support for the common practice of only using the prefixes that are integer powers of 10^3 (milli, kilo, mega, micro…) and avoiding, in most cases, prefixes like deca and centi. Of course, throwing Myria in once in a while (prefix: my, 10^4) does bring levity to an otherwise boring meeting, if you bend that way…

They are. Deciliters, centiliters, are used in cooking and drinking, except in english speaking countries which for some absurd reason insist that metric cooking must be done by the gram and if you must use volumes then it has to be the milliliter, which is completely awkward for being too small.

In reality the argument that you should only prefer powers of 1000 to avoid confusions is an issue made up by people who felt themselves really clever for finding a possible fault and proposing a solution to it without checking whether it actually is a common problem. Likewise, the idea that you should avoid using volumes in cooking comes from the idea that things like flour or sugar vary in density, so it would be a “better idea” – but it was merely a solution looking for a problem and now everyone exposed to the idea from childhood just accepts it as a matter of course.

That’s what many Americans have an issue with about the System International, it has these wee tiny units and these pretty big units. Measuring height or waist size in centimeters makes numbers that seem impossibly large, same for weight. But then temperature in degrees Celsius or Centigrade always sounds terribly cool. Fahrenheit degrees seem a ‘better fit’. Then there’s the fact that in whole degrees the Fahrenheit scale is 80% more precise so going to half degrees is good enough for all but the most finicky of precision uses.

We’re used to mixing units in a single measurement. Five foot, nine inches. I never see someone’s height listed as seventeen decimeters, five point two-six centimeters. They always go by 175.26cm – and we scratch our heads with no intrinsic grasp of roughly how tall that is.

Around when the Carter administration attempted to metrify the USA there was a show on PBS with some boy and a male adult traveling around and having the kid measuring things and doing comparisons with Metric measurements. But the production had one big flaw. Most things were ‘about’ so many metric units. A pizza measured about x number of centimeters. They went to an Indian reservation and the kid had to measure the height of a dam that an Indian told him was “two people high”. He estimated the Indian was about two meters tall so the dam must be about four meters. (Hey kid! How about demonstrating triangulation with a meterstick?)

If the purpose of the show was to introduce Americans to this measurement system that was supposed to be easier to use and less prone to errors in use – all those ‘abouts’ made it a terrible failure.

Hum your initial argument is that it’s more familiar so a measurement in imperial, is something you can figure “about” what it is. …. then you rail against someone doing the same with metric and make it metric’s fault.

Your “fit” argument and bigger and lesser values is illusory too, how can you seriously argue that say measuring your collar size in cm at 40cm would be “way too high a number” but then claim Farenheit is just right on a 90 degree day, or say 185cm makes something way too big a number tall yet have to boil your water at 212 degrees.

Um…. The people that ‘made this up’ are engineers, scientists, and, well, the writers of SI. References? “The prefix hecto- to centi- are not ‘preferred prefix’ but referred to as ‘other prefix’ by SI” (https://www.simetric.co.uk/siprefix.htm) “The prefixes deci, deka, and hecto are rarely used; prefixes that are multiples or submultiples of 1000 are generally preferred” (https://www.nist.gov/document-15694). The word preferred does not mean that others are prohibited when they are the most logical for a purpose (such as the aforementioned decibel) or are entrenched. But, if you read the supporting documents for the SI, the logic is there and clearly stated. Yes, there was a little of ‘how many prefixes do we really need’ and ‘we want them to be one character’, but that was in the 1930’s, well before SI.

In Australia, we very rarely see deci-, occasionally we see centilitres on imported liquor.

But our recipes do use volumes, by the “cup” (defined as 250ml, commonly seen in 1/4 and 1/3 increments), the “teaspoon” (5ml), or the tablespoon (either 15 or 20ml depending on who you ask, which is a bit annoying but generally doesn’t matter).

>”Um…. The people that ‘made this up’ are engineers, scientists, and, well, the writers of SI. References? ”

Again, these recommendations appear to be without any rhyme or reason, instituted “just because”. This seems to be an anglophone phenomenon, and other countries have no troubles using centi-, deci-, even hecto- units. Beer barrels come in hectoliters.

Like the NIST document you linked, which declares the centiliter as an “unacceptable unit”. Why? It’s perfectly acceptable elsewhere.

I can’t seem to find any first-hand source to declare that only the powers of 1000 units are to be preferred in SI. It’s always either some US or UK standardization organization that makes the claim but then doesn’t back it up. The wikipedia article making the claim ends up with a dead reference, and then everyone else references wikipedia verbatim. The source that wikipedia points at is again a US organization (WBDG) representing the building industry which have their own preferences and standards and don’t represent the SI directly.

So it still seems to me that this issue is still made up by latecomers to the metric system, who adopted some internal standards for their own convenience, and then others took that up as universal rule – and in the process undermined the point of the SI of having convenient units for all sizes.

While the building industry may avoid centimeters to avoid easily missed decimal points, there’s no reason why we can’t measure drinks by the centiliter – it’s not a reasonable rule to “prefer” 10^3 everywhere.

Point being, that cl is precise enough for the purpose. You don’t really care if there’s an extra spoonful of cola in your can, and frankly it’s unlikely the factory can reasonably control for that either, so 330 ml instead of 33 cl is too precise – the extra zero in the number is superfluous.

That’s another thing the johnny latecomers don’t get. They insist on being precise and using decimal points everywhere where they don’t matter, and then when the decimal points become a problem they use a more precise prefix. My height isn’t 176.25 cm or 17625 µm because the extra quarter cm is well within the daily variation of how much my spine compresses from just standing around, or what sort of shoes I’m wearing if any. It’s just extraneous information that has no real meaning or purpose.

It’s like the problem of buying a pound of beef, and complaining that you now have to remember to buy 453.5924 grams of beef instead. Just buy half a kilo and eat it.

@Galane:
That’s what me really disturbs with the imperial system: Your mix of seemingly unrelated units, which are not even powers of ten from each other. You mix foot and inches or miles and yards and there is no common divider. It would be not so important if the base unit is off by a factor of 2,54 or 3,3 (ft – meters).

And with wires it gets even worse: this AWG numbers seem really arbitrary. Somewhat logarithmic, but not really and not linear also. I know that they come from the production (wire drawing) but I can’t see, why a production process – which has probably changed several times, since this numbers were defined and probably got more efficient – shall be used to measure the wire size.

For me this units look so arbitrary and yes, the engineers who were able to fly to the moon with such a system really have earned admiration.

Maybe decimeters are a bit obscure, but when is the last time you saw millibels or centibels, or even Bels? In my experience, it’s always decibels. So much so, that there are people who don’t realize that a decibel is a tenth of a Bel.

The are is another unit that, in practice, is tied to an unusual prefix, as the hectare.

Bel/deciBel – Is that the straw??
A logarithmic scale expressed with decimal values?
Is 1 Bel =10 decibels or some other value – Make my head hurt…
Also, should it be mm or mM? Metre always seems to be capitalised.
And a meter is either a display module or a measure of tempo – at least in my experience :)

Yes, a bel is 10 decibels (it’s just decibel, no capitalization of the B. The capitalization is just in the unit). That’s why the formula for dB is 10*log(power/reference level). The formula for bels (just B) would be log(power/reference level).

The ease of centiliters and deciliters in cooking comes from the fact that many receipes call for ratios instead of exact amounts – for the point that you might be cooking for different numbers of people instead of always for three or four.

For example, 1 part of water to two parts of flour for making pizza, or 1 part of butter/shortening to three parts of flour if you’re making pie crust. Your preferences may vary, but if you have 250 ml of flour, what’s 1/3 of it – 83 ml? How do you actually measure it?

Instead, you take a 1 dl measuring cup, pour three dl of flour, and then stuff the cup with 1 dl of butter, and that’s how we do the cooking. We don’t bother with measuring to the milliliter or to the gram – that’s just pointless complication.

I remember hearing such as error on a police scanner where the office report the description of the offender as carrying a 300cm knife. Some quick witted fellow officer replied “That would be a sword?”.

“A HaD columnist screwed up the metric unit multiplier on a piece in the last month.” That was me! And I blame the centimeter, which is an abomination in an otherwise rational powers-of-1000 system.

Worse, I’ve messed it up before, IRL. I cut a 19 cm hole once because it was meant to be 15 cm + 2 mm padding on all sides. Yup. Nowadays, I try to keep everything in mm anyway. The centimeter is kinda silly, because even in woodworking I can get sub-mm precision. So it’s always like 14.5 cm instead of 145 mm. Boo, centimeters!

(On topic: I mix units all the time. American living in Germany. Doing PCB layouts. You can’t win. You learn to live with the dangers.)

The stadia in various texts from the time of ancient Rome. It might have been a useful unit, if it weren’t for the Romans’ habit of constantly renovating the stadium in question and changing the length of the unit. And it took a while for people in far-flung corners of the empire to find out about the latest public works program. So how long the writer meant for this to be not only depended on what year the text was written, but how far behind the times the writer was.

On the smaller scale of linear measure, there’s the barleycorn. While it’s a pretty handy way to measure things if you’re on a barley farm, I suspect the variety of barley grown and the condition of the soil could throw off your calibration.

Some charts of Imperial liquid measure listed the smallest measure as the “mouthful.” Not in my kitchen, you don’t!

In the United States, at least, real estate and timber land is still measured in chains (66 feet), because 10 square chains happen to be the same an an acre. Outside the surveying and timbering community (and landowners like me who interface with them), it’s a pretty obscure unit.

Not really invalid, but a “Dash/Splash” always amused me.
Particularly if the aforementioned dash involved alcohol, as it seemed to get progressively larger over time.
I vaguely recall some form of radial measure, I can’t remember the context (it’s very old), but something to do with calculating distance travelled from a fixed point (e.g. observing a ship from a point on shore). Basically it had no relevance to anything except to objects travelling the same course at the same distance, and hopefully being approximately the same size, as there was no reference to scaling the observed object…

6400 mils/circle vs 6283.185… milliradians/circle. (Once we are all SI, we can concentrate on the pi vs tau argument.)

So if you are 10 meters off at 10 km you can crank a mil to the left and still be close enough, but if you need to point in the opposite direction or at right angles, 3200 or 1600 is easier than it would be in milliradians.

I always consider the measure of how useful a system is as how well it plays with the rest of the units in its ecosystem. It doesn’t really matter what archaic amount the measurement is based off of, we can always preserve that with a few precisely-machined metal spheres on display in a museum somewhere. No biggie.

But how many ounces are there in a stone? How many eighths of an inch in a yard? Quick, how many? Well, let’s see, eight times twelve times three.. And the weight conversion is sixteen times fourteen… Dear god, why? Sure, conversions are pretty simple math, but why is it so needlessly ambiguous? Base it all on ten, like the counting system the whole world uses. I was raised with the ‘murcan system, but the time I’ve invested in learning metric has payed enormous dividends in time saved.

In scientific and industrial contexts metric is the clear choice. Precision and conversion is essential. Having a feel for estimating the measurements matters less because it is all done mathematically.

In everyday life conversion and precision are almost completely unnecessary. Who cares how many yards are in a mile. Your directions will be in 1/2 miles. All that is needed is the ability to estimate measurements. Therefore, at home, you should use whatever you know and whatever your neighbor understands. It makes no difference which system that is.

Although I use them in scientific contexts, I have no feel for how far a kilometer is or how 20C feels. It is very expensive in terms of time and effort for me to learn intuitively what these units mean and there is almost 0 benefit to do so. At work I can use metric because it is efficient. At home I use Emperial and it’s inefficiencies don’t matter.

Kindof. Astronomers use convenience units far, far more often than metric, because originally, they isolated out the inaccuracies of the calibration. Not the easiest thing in the world to compare a star to the international prototype kilogram, after all.

…. as you would if you were McDonalds buyer securing supplies for a decade, but I guess at the grocery store you’d be more like “I’d like point zero zero zero zero zero one yoctoAMUs of apples please.”

“It is very expensive in terms of time and effort for me to learn intuitively what these units mean and there is almost 0 benefit to do so.”

When we switched from the Franc to the Euro in the early 2000s, conversion rate was 6.55957fr/euro. Seemed like it would be a nightmare, but actually, most people except maybe a part of the elderly population, have been doing just fine with this new ‘unit’.

In the beginning, you always had to make conversions in your head to get a feel for how much does this item cost in your old currency. After some time, this becomes natural.

The effort wasn’t that hard. But it was “imposed”, we didn’t really have a choice, just an accomodation period.

Obligatory metrification ? In the US ? There’ll be a new revolution.

NB : no, I don’t want to enter a political argument, I just don’t remember how the Maastricht treaty etc… worked, I just now that in 2002, there was no more choice, the Euro was happening

I estimate the affordability of the stuff I need or want as a fraction of my income, not in bananas. Grocery bags are variable (do I have a dinner party ? has the price of milk changed ? not gonna be home that much this month …) For a lot of us in the real world, the salary stays the same month to month, and guess what, it’s the only flow of money coming our way regularly. Silly us, having a full time job with a bit of security.

Well some countries have people who feared the shops would rip them off, and indeed with some product they did raise the price hidden by the new coinage, but it wasn’t as bad as feared.
But anyway, people wanted to keep the old price in mind to make sure, so they had to do conversion sometimes.
That’s not silly but practical.
Mind you I heard about people who used their old coin as reference half a decade or more later, and that’s just silly, especially since it doesn’t account for normal inflation.

Under “becoming natural” I understand: You just know what a liter of milk costs, e.g. around 1€. So it’s cheap when it costs 90ct or expensive when it costs 1,45. But you very very rarely convert or compare (also not be “feel”) to the old currency. And 20yr later, if you “accidentally” convert, you are shocked anyway because you realize the inflation. And those crazy guys from the EZB (european central bank) still want to increase it! They should be replaced by more competent persons.

A lot of us still do that exercise regularly. When I am in the USA I add a third, in China I divide by 5 and in the UK I double it. Never in those countries long enough to really work directly in their currencies or I would have trouble when I get back home. The zero benefit argument is probably valid. One nice thing is with newer US hotels you can change the AC settings to metric and set the temperature just where you really want with less effort.

US has lower tax though, and that system where they pay people partly through tips (outrageous example of bad capitalism).
So you can’t just convert the coin exchange rate and get a realistic view of prices.

As a technical minded person I don’t see any benefit in “warmth and character” of units. I prefer them precise and easy to work with. You are allowed to call that “cold”, but for me that’s what a system of measurement has to be. Cold, precise, unbiased, scientific.

“My” problem with measuring length in inches is that it seems to use fractions over decimals. Now 1/2 inch and 1/4 inch are not that painful, but 5/16ths is just weird to me. And while measuring, counting the tiny gradations is a nightmare.

It is possible that I’m just slow and have poor eyes, but I don’t have these issues with metric.

Sometimes I measure stuff in metric and convert it to imperial, but then people look at me funny when I mention inches in decimals instead of fractions.

The reason for these fractions is because a long time ago it was much easier to do calculations with fractions than decimals (hard to imagine with calculators and computers today). If you want a mathematical example just look at how many factors there are for 96 vs 100.

The survey grid for most of the USA is fixed to a massive arrangement of mile squares, AKA sections. Homestead plots were allotted in quarter sections or 1/4 of a square mile, or 160 acres. Trying to shoehorn kilometers and hectares into that grid causes a big mess.

It’s already bad enough where adjustments have to be made to accommodate the curve of the Earth, or where when a town was founded along a river the surveyors made the practical and logical choice of aligning streets parallel and perpendicular to the river – then decades later some nuts decide, no, the streets should all be aligned north/south and east/west. That’s why so many cities with a river running through have an old core with the streets kattywampus to the surrounding zones. Thus they have odd shaped blocks where one can try to drive around the block and end up two streets off from where you started.

That’s cute, you should see Southern Ontario, we’ve got basically a triangle of 3 lakes, the later grants of 160 acre sections over older 200 acres sections, all over the top of and in between old French feudal arrangements https://en.wikipedia.org/wiki/Seigneurial_system_of_New_France aligned maybe against either of 3 great lakes, or true north or compass north, or various rivers.

Oh yah and before the English got organised the tendency of some of the older settlements to develop radially, roads on a spoke and hub pattern, but tending to wander along the easiest contours or around obstacles.

To some people I am Mike to others I am Michael I don’t find it difficult to use different units to describe myself why would it be harder to use different units on the outside world?
Tools however are harder having to own two sets.

Having an intuitive feel for a unit is something you only get with use. As a brit I don’t have a grasp of weights in pounds, or temperatures in Fahrenheit, but I’ve managed to get a good idea of a person’s weight in kilos and height in meters/centimetres just by using those units (I suppose measuring other things using kg and cm helps).
It’s not that difficult in terms of time and effort to internalise new units. Start by comparing things you do know, to the units you want to learn, perhaps by carrying around a thermometer with both C and F scales, and trying it on different things.
I think we can all agree that knowing BOTH imperial and metric, is better than only knowing one or the other.

I wanted to get an instinctive feel for the system of measurement I used in my work, so I set up my odometer and speedometer to show kilometers, set my phone to display metric for maps and temperature, set my scale, my thermostat, got a meter stick instead of a yardstick, set up my oven to display C, etc.

It took surprisingly little time to acclimate, and believe it or not it’s been useful. And I’ve already noticed it’s rubbing off on some of the people I hang out and build with. It’s going to happen in our culture eventually, may as well embrace it.

Or when people try to import files from Inkscape to our LaserCut software and things come out 25 times too big or too small due to the Inkscape DXF plugin not respecting our choice of inches or millimetres.

This article is really dumb. Sure, units have equivalencies and one could in principle work in any unit valid for the measurement… That is NOT the point. The point is that 99% of the globe has standardized into a set of units, the SI. The SI is simpler to use too (only powers of 10, no 12 in per foot, 16 oz per lb, 5280 ft in a mile, WTF??). So, to do any technical or scientific work in units that are not standard is plainly stupid. (Sure, there are legacy factories and equipment that still work and one should keep using, but this has to stop some day… no more new equipment in non-standard units…)

Well, Most U.S. manufacturers have switched to Metric fasteners over the past 4 decades…
But replacement nuts/bolts/screws and wrenches still need to be made for existing equipment.
And then I think about “standards” that have been around a long time, teaspoon, bolt of cloth, bushel…
There are literally millions of highway signs and “mileposts” in the U.S. that would not only need to be replaced, but also relocated, if highways and autos were to go kilometer, and the decades necessary for dual signage until it is deemed “safe enough” to drop the mile unit.
While we’re at it, let’s get every country on the same voltage, outlets, and frequency for electrical power, and make all vehicles/roads left or right hand drive, everyone use the same currency, and same ammunition.

There is a NATO standard for bullet size, and many countries did in fact move to a unified 230v mains because of the EU and such, while in general all over the world it has been either around 220v and 110v and 50Hz or 60Hz, so pretty standardized. And many moved to IEEEC outlets. Russia even has the same outlets as Albania, Austria, Belarus, Bosnia and Herzegovina, Bulgaria, Chile, Croatia, Denmark, Estonia, Finland, Greece, Hungary, Iceland, Indonesia, Iran, Italy (standard CEI 23-50), Kazakhstan, Latvia, Lithuania, Luxembourg, Republic of Macedonia, Republic of Moldova, the Netherlands, Norway, Pakistan, Portugal, Romania, Serbia, Slovenia, South Korea, Spain, Sweden, Turkey, Ukraine, and Uruguay.

Yet in Japan half the country runs 50Hz power while the other uses 60Hz due to the post WW2 electrification of the entire archipelago being split between American and British contractors. Thus all electrical and electronic equipment used in Japan is either manually switchable or uses an automatic adjusting power supply.

So for those laptop power supplies where you can go anywhere in the world and only need a simple dumb cord swap to use any voltage from 100 to 240 and any Hz, you can thank the guys who couldn’t decide on a single standard for Japan over 70 years ago.

Not entirely right in that UK was 240V, Europe was 220V and 230V. The standard is 230V with a wider tolerance than before, so in fact the vast majority of the UK is still at 240V and France etc at 220.

For single phase or old school delta 3 phase – much of America is 120/208 3 phase at commercial levels – and then 277/480 or 347/600 for higher voltages.

I use Alfie’s when pulling lengths of wire to pull (I’m an electrician – try not to be a sparky to much) 1 alfie is a full arm lengths without stretching out to much – 1 alfie equals 5 feet. Works great, easy to do the math on multiples of 5 and is pretty transferable- my apprentice uses marks as his measurement

Standard “ammunition”? You just know straight away you are dealing with an American when they are worried about ammunition standards. News flash, the rest of the world doesn’t care about ammunition unless you are a hunter, farmer or in the military.

” The point is that 99% of the globe has standardized into a set of units, the SI. The SI is simpler”

Oh, for crying out loud. The advantage of SI has nothing to do with its units. It has to do with the fact that there’s a common standard for what a measurement is, and there are as few of them as you can possibly have. Imperial units have metric definitions, so the imperial measurements are just convenience units. And convenience units will always be around.

And there are still plenty of bizarre convenience metric units. Chemists measure things in debyes, which is 1 x 10^-18 statcoulomb-centimeters. Try to figure out what that is in SI units.

“The debye is still used in atomic physics and chemistry because SI units are inconveniently large. The smallest SI unit of electric dipole moment is the yoctocoulomb-metre, which is roughly 300,000 D.There is currently no satisfactory solution to this problem of notation without resorting to the use of scientific notation.”

And come on, how hard is it for SI to simply introduce a named unit that is a more usable size.

And Angstrom is not SI but still metric, so at least you don’t get a mess because of its use.

What a BS! Have you ever heard about, mili’s, micro’s, nano’s? Never? Too bad, because these are able to render “inconveniently large” SI units into surprisingly small. All these “Angstroms” are still here because of shithead nazis, who have a pain in the ass because local dead heros are getting lost in vein hurting shithead’s pride.

@moe as I said ‘The smallest SI unit of electric dipole moment is the yoctocoulomb-metre, which is roughly 300,000 D.
And with yoctoCoulomb the yocto denotes:

Yocto (symbol y) is a unit prefix in the metric system denoting a factor of 10−24 or 0.000000000000000000000001.

So yeah we are way way below ‘nano’ there. And therein lies the problem.
For a convenient list of subdivisions see this link https://en.wikipedia.org/wiki/Nano- and notice that yocto is in fact the smallest subdivision in the lineup nano – pico – femto – atto – zepto and finally yocto

As for your Nazi remark regarding angstrom, Anders Jonas Ångström of course was a Swedish physicist, who died in 1871, so I’m not seeing a link to Nazis, nor do I see some theoretical cabal of Swedish nationalist being able to get people to use angstrom.

>”Anders Jonas Ångström of course was a Swedish physicist, who died in 1871, so I’m not seeing a link to Nazis”

The Swedes were pioneers of scientific racism and eugenics, which gave backing to the Nazi racial theories. Plus they bent over to the Nazis in WW2 while pretending to be “neutral”. Under the overcompensatingly kind welfare state, they’ve always been little hitlers who feel themselves superior to others.

“And come on, how hard is it for SI to simply introduce a named unit that is a more usable size.”

Look, you’re missing the entire point here. There’s a perfectly good unit that is strictly defined that they’re using. There’s nothing wrong with debyes. There’s no reason to redefine them, because there’s almost *no* reason to ever need to know what a debye is in terms of coulomb-meters. The people who do need to know that have to take care in the conversion, but there are fewer of *those* people than there are the ones making measurements in debyes.

The point of SI isn’t to create a “one size fits all” set of fundamental units that everyone uses, no matter what. That’s idiotic, and absolutely no one wanted that when the metric system/MKS/SI was created. The point of SI is to create a set of fundamental *references* that all other units can be *referenced to*, and ideally to create a system where you can make ‘secondary references’ that are all equally precise. (You can do that with most of the SI units at this point, but not mass yet – mass is still referenced to the IPK). It’s absolutely hilarious to hear people “defending” the metric system units because “oh, it’s just powers of 10” like that magically makes the units useful.

Before the metric system/MKS/SI, different systems would have different references. There was an Imperial yard standard, for instance – an actual physical brass rod. The British one was stored in Parliament, and at one point was destroyed in a fire and there had to be an entire commission to recreate it, using specific metals and very detailed construction.

*That’s* what SI was designed to replace, and it’s done an awesome job at that, except for mass. Nowadays creating a standard yardstick is easy: a yard is exactly 0.9144 meters, and a measurement of length in terms of meters is a matter of interferometry and atomic timing, since length is determined by the speed of light, and time is determined by the atomic transition frequencies.

Feet, inches, yards, miles, light-years, parsecs, angstroms, astronomical units – those are all perfectly fine convenience units. A foot is a damn good convenience unit, too, since you end up with the speed of light being 1 foot/ns to within 2%.

Come on are you really try to tell me that fractions of an inch, inches, feet, yards and miles are are easy to move between that mm, m and km? Moving a decimal point three places is always going the be more convenient that multiplying and dividing using arbitrary numbers. Same goes for cups, pints and gallons vs ml and l.

As a lifetime user of the non-metric system I can write with complete certainty that it is rare to move between the units. While conversions are in place to anchor them one to the other, each one simply occupies a particular scale in the same way that kilo and milli do. When was the last time a metric user paced off a kilometer with a thousand increments of a meter long stick? Same thing with miles and feet.

In OZ during the ’70s it became almost impossible to purchase dual scale ruler/tape measures.(metric only)
Unfortunately, a lot of building material was still sold in imperial units.
This made life “interesting”.
My house, built during this period has 3 different door sizes, 1 for external, and 2 different sizes for internals.
Externals are still available, neither internal can be obtained “off the shelf”
I believe the bricks are imperial, but the brick tiers/building height are calculated in metric… (sigh)

Jenny, a great article – thank you. This is a good example of how to discuss popular topics in public without resorting to controversial views in order to generate a response. “If you curate genuinely interesting content, they will come”.

My own experience of where units meet: learning to paraglide, I found it interesting that altitude is measured in feet but horizontal distance is measured in metric units. The explanation I was given was that it would be too risky to attempt to switch the world to metric altitude measures.

Yeah, but the difference is that feet sound like zimbabwe dollars to metric users. Anything that’s in the tens of thousands quickly becomes too big to comprehend ™ so it’s basically a meaningless number. Is it high or low, who knows.

4.6 kilometers however is pretty high. That’s like, from my place to downtown, but in the vertical direction.

I could get up to 74MPG in my 14 year old Smart Pulse on a long journey (though with normal unleaded it maxed out at about 63). In the UK, cars generally achieve pretty high MPG. At 70MPG that’s 91 g/Km which means he’s either got a Smart car and he’s driving it like I did :-) or he’s driving a hybrid of some sort. The average CO2 g/Km in the UK for new cars is currently 120g/Km2 = 56MPG.

Also to be remembered is that UK gas is 96 Octane RON, and despite the 1 or 2 point discrepancy between the RON and RON+MON/2 methods of stating octane, that’d still be 94 in US whereas premium is 91. Anyway, means motors can be made higher compression and achieve greater efficiency. That’s why high mpg euro models come over to north america and have the spark timing wound back to survive on 91 and the mileage sucks donkey bollocks.

It’s funny, the US having non SI units is disruptive because the US is big and influential due to its economy, but their size and influence is also the reason why they feel so entitled to ignore a universal standard.

What the SI people should do is set up a very large building in the US and introduce the US-I standard and make it exactly the same as SI but make the US feel they have their own thing.

Almost… what we should do is take a a chainsaw, and alter your president’s armspan to 1m. Then you could claim the new greater American yard with him as the golden standard, and the rest of us could just call it the metre.

They don’t have Russian tires. But once I was in position – best to tell them you want to draft – when my windshield began to get wet with fuel. I pulled around and he had lost the cap to his tank and the air flow was pulling out a steady spray. I caught the driver’s attention, reached out my side window and rubbed the glass then rubbed my fingers together and it must have communicated OK because he pulled over immediately.

In the US lorry’s drive at 85mph! Gee I wish UK lorry’s went this speed, the amount of time I’ve spent stuck for multiple miles behind two lorry’s, one going 60mph and the other doing 60.2mph, as the slightly faster one attempts to over take the slower.

Actually on second thoughts, all that mass travelling at 85 sound pretty dangerous.

Wow, that is nice. I had a 1958 Alpha Romeo and it got a steady 40mpg on the highway at 75mph and that would include going over a mountain pass. 1970’s IIRC. At a time when US heavy street iron got 12mpg, like a Roadrunner. Maybe 6mpg if a teenager is driving it.

I get between 91 and 94 MPG (imperial, or 3.0 – 3.1l/100km metric). Officially the car’s supposed to be 3.4l/100km motorway, 3.6 mixed. No surplus batteries to add weight, just the one to start the engine… Not a particularly small car either. Can ya guess what it is yet? ;)

In my country, we use mixed units as well. Imperial for woodworking, water and electrical pipes.. Distance and weights in SI. Eggs ? Sold as a dozen, not as 10. Thing is, units must allow communication with the “other” ( people, engineer, etc ) . Which they are is mostly a question of convenience or personal preference.

As for the Mars mission, that would involve more blame in the lack of rigorous testing than the units. If it had been tested correctly, a difference of about 2.54 times in a value should have been detected earlier. My bet is that someone believed ( or laziness ) in some other people assertion of “previously tested” and skipped doin their own tests / calibration.

Similar to the cock-up that destroyed the first Ariane 5 rocket. Assuming that your space vehicle will “just work” because all the individual pieces worked OK in previous vehicles, so there’s no need to spend time and money doing at least one ‘all up’ test, right?

Foot-pounds and inch-pounds is typical. SAE bolt torque in inch-ounces is typically reserved for bolts 1/4″ shank diameter or smaller.

But there are those cases where someone is too lazy to do their fraction math to change to units appropriate for the bolt. Like measuring everything in centimeters, even rather large things, it would be possible to specify the torque on every bolt in an engine in inch-ounces. Problem is, nobody makes a torque wrench calibrated in inch-ounces that’s capable of measuring over 5 foot pounds or so. Most inch-ounce torque wrenches are 1/4″ drive.

Ha! There’s another use of Imperial units that’s likely never ever going away. Square drives for sockets are 1/4″, 3/8″, 1/2″, 3/4″, and for the bigguns – 1″ size. Available anywhere in the world so sockets bought anywhere will plug onto wrenches bought anywhere else.

Car Rims in inches but the tyre measurements are metric.
except for the poor ol’ TRX rims and tyres.
e.g. 14″ by 7″ rim with 205(mm)/60(ratio – for gods sake!) tyres.
My tyre fitter STILL has to do multiple conversions to ensure rolling radius/circumference are suitable – spec for ABS/DSC equipped vehicles.

I had a Chevy S10 blazer once, now thankfully long gone. I had to have a full set of metric and SAE sockets to work on that thing. What a nuisance!

And for those folks that use topographic maps. The 7.5 minute series in the US uses a mix of feet and meters. This is the greatest nuisance when you are working on the edge of two sheets, one in meters, the other in feet. I have often wished that whoever decided to do the new maps in meters was available in a dark alley to be beaten. Even when working on one map, I would much rather have elevations in feet. My mind is calibrated in concepts about what it means to cross a pass at 9000 feet versus a pass at 12,000 feet and such like. Here the historical precedent of having thousands of maps already in feet and no possible plan to convert them all to metric should have carried the day. Consistency trumps idealism.

As for the Mars spacecraft in the original posting – this is just sheer incompetence. Every experienced engineer knows to check and verify the units being generated by any device they are integrating. At least I certainly do. So this is a botch on at least two levels, the second being inadequate testing. We live in a mixed unit world and likely will do so for the foreseeable future.

Yah, I’ve found a few 3/4 and 5/8 on “all metric” dodges and fords… Plus in the last 10 years it has got super prevalent that 3rd party replacement parts don’t give a crap if your car is metric or imperial, they supply whatever they feel like, leading to metric heads atop imperial threads or vice versa. They get thread right where thread is on the car, like tapped hole in the block or whatever but the parts on the parts might be anything.

In various EU countries they apparently mainly use (ANSI) imperial for plumbing screw connections. You get connectors for taps and pipes that are inch-based (while sometimes also use the local name for inch simultaneously). While the pipes themselves are metric.and soldered connections are also metric.

Plumbing sizes are a mess! The commonly used pipe size standard is actually IPS for Iron Pipe Size. Drain and waste plastic pipe uses sizes close to IPS, considered equivalent. Plastic water supply pipe is *mostly* sized to be compatible with IPS. There’s a second sizing system for PVC pipe that matches up with the size system for copper pipe. That pipe is labeled CPVC, the C in front indicating it’s CPS sized.

There’s a bit of confusion that CPVC means something about a different composition of the PVC that makes it able to handle hot water, fostered by the fact that *most* CPVC pipe is the tan colored higher temp plastic. But you can, if you really want, get CPVC pipe made with the lower temp white PVC.

This requires special size adapters when joining IPS size PVC to an existing copper pipe plumbing system. The easiest way is to solder an NPT (the thread standard for IPS) threaded copper nipple onto the copper pipe then screw on a threaded PVC adapter and get to gluing the PVC together.

But no matter what pipe size system or schedule (wall thickness), among *all* of it you will not find a piece of pipe or fitting where an exact 1″ diameter falls between the inside and outside diameters. The ID is always over 1″ or the OD is always under 1″. Years ago I had a project which required a rotating electric contact ring of precisely 1″ OD. I figured I could get some piece of copper pipe or a threaded brass fitting to bore and turn. Nuh-uh and nope! Not even the heaviest schedule copper pipe would do. The “one inch” had an ID just a titch over 1″ while the next size down had an OD less than 1″. Standard schedule 1″ copper water pipe is significantly larger than 1″ ID.

I ended up using a fitting off an old propane catalytic heater. 1″ lay comfortably less than the across the flats dimension of the hex, and after the threads were bored out there was enough metal to make the thickness of the ring match the original. When it comes to gas fittings, someone who was involved in setting the standard knew what an inch is.

That’s on the “Things to fix with a time machine.” list. Take a bunch of precision dial calipers and other measuring tools back to when people were establishing standards for pipe sizes, and demonstrate the proper measuring of diameters so that 1″ pipe will at some point be exactly 1″. None of this “nominal” size BS.

Actually the C in CPVC stands for Chlorinated which makes it suitable for higher temperature service. They just happen to sell it in tubing sizes instead of pipe sizes because it is usually used where copper tubing was used in the past.

I’ll throw in on this on. My property boundary (small property– 700m^2, roughly) is specified on the official deed using: feet, chains, a different chain (railroad), and yards. Oh, the feet and yard are surveyors feet and yards, not standard feet and yards– they differ by about 2 parts per million. Not to mention the angles (true, magnetic, and relative to baselines between landmarks, some of which no longer exist, depending on which division of the original tract was involved) Tell me that adding meters makes it more difficult again?

I dread to even consider the nightmare of cross-code or cross-platform consistency, which is probably where it all went screwy.
but yeah, billion dollar toy – please make sure everything works.
I would have thought a comprehensive simulation would have uncovered an issue.

I work at NASA and I’m appalled that we still do anything in Imperial Units, but we do. I’ve also noted the ubiquity of decimal inches in some areas, such as electronics, where a common component lead spacing is in 0.1″ units. Using decimal inches gives some of the advantages of SI, but without the pain of a new base unit.

Yeah it’s a thing all over the world including the EU that spacings in electronics often use imperial pitch.
I guess it doesn’t help that various tech-active Asian countries have a British history to them too.
Still though, since it’s worldwide at least parts are widely available everywhere in those units so in practice it’s not a big a hindrance as some instances of the imperial unit.

Actually the inch was redefined to be exactly 2.54cm, so it doesn’t really matter. One mil is exactly 25.4um. You can easily store imperial values in a metric design with no loss of precision. A 0.100″ pitch header is exactly 2.54mm.

However, you cannot go the other way. A 0.5mm pitch QFN is 196.850393701… mils. If you try to use a metric pitch in an imperial design, you lose precision.

This makes not only makes the transition to metric much easier for US PCB designers, but it also just makes sense so all your numbers are bang on without loss of precision.

That’s actually a sound point.
Although with spacing in traces and connectors you would think it’s about the power that can be delivered and crosstalk and parasitic and dielectric effects and more such practical things though.
I mean 1.27mm is 27% more than 1mm and that would play you’d think

Heh, I’ve actually seen designs that pull this shit on large packages. No, 0.4mm is *not* 1/64. It’s 0.015748. 1/64 is 0.015625. The difference may seem small to you, but after 100 pins, you are off by an entire 0.3125mm.

Yup, the entire thing just seems really dumb. It doesn’t matter that one of the units was imperial and one was metric. Just that the value passed in an API wasn’t well defined or checked. You’d have the same issue if one piece expected km/h, but the other piece passed m/s…if one used signed and the other unsigned…one float, the other fixed…etc. Much embedded software doesn’t even use units as is, they often work on the scale or the scale of plausible values to fit the most precision in the smallest amount of space.

If your thingus is never going to work with negative numbers, don’t use signed variables. Not using one bit for indicating positive or negative increases the maximum positive value the binary number variable can hold.

A classic example of “Should have used unsigned.” is in the spice counter in the Dune II game. If you harvest over 64K spice, the counter rolls over and starts displaying data from some other chunk of memory. Apparently somewhere else in the code an unsigned integer was used to store the count because at the end of a level it correctly displays scores over 64K.

Funny when it happens in a video game. Not so funny if it makes your rocket try to be a Catharine wheel.

I wrote a scientific library that meticulously documented the units and the minimum, maximum and default values for every parameter in the header of each file. A GUI programmer complained one day that my code had crashed because of a bug. I went back to my office, ran the code under the debugger. I then went back and told him that his units were off by 10**6. That was it. No theatrics or recrimination, just, “It’s your error, you’ve got the units wrong.” I was quite stunned when the project manager called me on the carpet for “not being a team player”.

The team did lots of metrics and the GUI boys spent 7 man days for every man day I put in. The interface was breath taking. It would draw one curve, erase the screen and draw two, erase the screen and draw three, etc. I sat with another scientist who was doing QA for the team and he giggled like a school girl as the screen flashed while drawing the typical 6-8 curves a user would need. I felt like crying.

A few months later the company was bought and split up to meet antitrust regulations. One of the acquiring companies got the package we were building. I heard from friends whom I knew there that they kept my scientific library but threw out the GUI.

The Mars probe incident is really an example of inadequate integration testing. Unfortunately, that is NP Hard. So it comes down to professionalism, or the lack thereof.

I am sorry, but for Navigation SI units are not good. Nautical Miles and Knots are appropriate and related to the earth being divided into degrees, minutes, and seconds. This is the standards all over the world (except Russia) for aircraft.

Nautical miles and knots don’t make navigation easier. European glider pilots are using all-metric just fine. There just would be horrible accidents the day standards were switched. Imagine a Boeing 777 flying Mach 2 on its way from northern America to Europe via the south pole.

Gimme a GPS and plenty of batteries, oh and a camel… (to carry the WATER, you sickos)
:D
I can read maps – scale don’t matter.. in this context…
I can’t use a sextant… except maybe to light a fire. (isn’t an accurate timepiece required?)
(a compass would be preferred)
A pacing stick is a pacing stick, metric imperial, or cubits. ( a length of cord tied between the legs works too – at least a stick can be used for support)
all units would be self consistent.
The most important instrument – the mush inside the head-box.

Nobody’s mentioned that other unit conversion that tends to bite, at least as measured by stack overflow — my personal take is that libraries that provide trig and linalg functions and expect bloody degrees as an argument are highly suspect by definition :-)

In the running for Grand Prize for “Units Inappropriately Large AND Some Crazy Irrational Size” is the Radian. Large? There’s 6-ish in a circle. Irrational? Since Pi is that wonderful unending irrational number due to the fact that the circumference of a circle is just a smidge over six times the radius of the same circle, a Radian’s size is also not a rational number.

Yet Radians are used to do various math type things. Why, when Degrees are much more plentiful and rational, thus there’s often no need to deal with pieces smaller than one? With Radians you’re always dealing with fractions of one.

Radians, the bitcoin of geometry, except they’ve all been found.

Whose idea was it to take Pi and use it as measurement of angle, and give it a different name too?

In Bob Shaw’s Wooden Spaceships series, the universe it’s in has the physics property that the circumference of a circle is *exactly* three times the diameter. But the reader doesn’t know that until the end of the third book, via an offhand comment about a complaint from barrelmakers after one of the planets gets transported to another dimension. Presumably they’ve been popped into our solar system – but the author died before writing book 4. :(

Screaming and kicking, I remember it well, for some reason we blamed the french.
I use both because some machines are metric and others imperial, so i lot of the time i just guess,
And then make another one, that fits.

“As a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. On 7 October 1790 that commission advised the adoption of a decimal system, and on 19 March 1791 advised the adoption of the term mètre (“measure”), a basic unit of length”

“The metric system was developed from 1791 onwards by a committee of the French Academy of Sciences, commissioned by the National Assembly and Louis XVI to create a unified and rational system of measures. The group, which included Antoine Lavoisier (the “father of modern chemistry”) and the mathematicians Pierre-Simon Laplace and Adrien-Marie Legendre, used the same principles for relating length, volume, and mass that had been proposed by the English clergyman John Wilkins in 1668″

Although:

” in 1875, the Treaty of the Metre passed responsibility for verification of the kilogram and metre against agreed prototypes from French to international control. In 1921, the Treaty was extended to include all physical quantities including electrical units originally defined in 1893.”

Serious question.
Do US Americans call their measurement system “Imperial”?
or is it something like US Standard?
I’m curious because I grew up with UK Imperial (both Decimal and Fractional), US measure (fluid), Metric,SI etc
and i can honestly not recall whether USA have a universal measuring standard.

It is commonly called Customary, sometimes US Customary or USC. All units of length, and units of mass from the pound down are reconciled. Fluid and dry volumes (gallons, bushels, and all multiples and subdivisions) differ. When volumes are expressed cubically (cubic feet, cubic yards, etc), they are the same. As we do not use the stone, hundredweights and tons are 100 and 2000 lb. Our gallon and bushel are based on pre-1824 units, the Queen Anne wine gallon and Winchester bushel. Where Imperial differs, it is not legal for trade in the US. However, many people, American and otherwise, call Customary Imperial by mistake. However, many industries metricated and use SI. It is the same for everybody (except minor spelling differences, meter, liter, deka-). So we use USC, SI, or a confusing mashup.

In 1969, the SAE Board of Directors issued a directive that “SAE will include SI units in SAE Standards and other
technical reports.” During the ensuing several decades, SAE metric policy evolved and implementation
progressed. The SAE’s current metric policy is, “Operating Boards shall NOT use any weights and measures
system other than metric (SI), except when conversion is not practical, or where a conflicting world industry
practice exists.”

Thanks for the corrections JohnS,
But just to (over)simplify, if you go to a big box store in the U.S.A to buy a set of wrenches[spanners] or sockets,
often the package will be labeled SAE or Metric to distinguish the two types.

And let’s not forget the Metric screwdriver!
(60 ml of orange juice and 30 ml of vodka)

Thanks, I feel guilty as hell now, when I saw those charity ads “Just 10 cents a day can educate a 3rd world kid.” years back I should have donated, and maybe there would now be a few less people in the world who are too ill educated to deal with fractions.

Seriously, how can anybody intuitively figure out what ” 10-63/64″ ” means? How am I supposed to even read such values without first getting out a calculator? Being educated doesn’t mean being a math savant who just quickly gets 63/64 = 0.984375 in his head…

Indeed sir, you are the great educated american. Many felicitations to you and your imperial member. Your measurement system is absolutely the best and by rights is the choice for all smart, educated, rainmanesque math geniuses like your own shining self.

The rest of us dimwits still have to get by somehow, and fractions like 63/64ths, or 5/16ths, or 3/32s throw us for a spin. Also, us third world types (i.e. people not from the shining beacons of USA, Liberia, and Myanmar) don’t see as well as your eagle-eyed-ness. Figuring which one of the three (four?) different types of gradations we are counting on a tape measure is too tall a measure for our poor stunted eyes.

Indeed, had you donated, we too might have been educated. But not to worry, I’m sure a kind, good-hearted samaritan like you will come perform all our projects for us.

No no. No pride at all. None whatsoever. Only a deep all consuming shame. Us metric cretins don’t deserve the privilege of pride. Indeed, it reflects favorably upon your educated, math wiz, eagle-eyedness to even be conversing a lowly being like myself. I will apply myself zealously to your instruction about describing lengths in fractions, giving up decimals, and counting 1/32nd gradations from a distance. I am forever in your debt for proposing to show me the light.

What’s ya problem, don’t have a Metric/Imperial Decimal/Fractional measuring tool?
In many respects Fractional can be good for manually resizing objects, just divide down to the smallest common value adopt the required scaling and the multiply back out – not forgetting the inch/foot corrections.
Easy, I say.
OR use a big pair of dividers and bugger all the annoying numbers – Anyone remember Sketch-A-Graph?

Only to hide the “k” in F = kma, the Imperial/Customary form of Newton’s 3rd law. There are three common ways to hide the k and pretend Imperial/Customary is coherent. Make up a coherent unit of mass, the slug, but try buying a slug of potatoes at the grocer, make up a coherent unit of force, the poundal, but try finding a pressure gauge in poundals per square inch, or a coherent unit of acceleration, the g, equal to standard earth gravity. Be sure to only use one solution at a time.

But most people just use the pound-mass (lbm) and pound-force (lbf) and bugger the equation. The best solution is to convert to kilograms and newtons and use a coherent system.

I got stung recently buying a replacement trampoline mat. ( in Australia a metric country since before I was born)
The mat size is sold in ft but the springs are in mm and 30cm isn’t close enough to 1ft to convert 4m into ft….

Do they use canvas for that though? For some traditional reason most canvas products (and polytarps since) are sold at cut size, not size they are after hemming and any shrinkage. Anyway, you’d get your 4m pad and find it was 3.8, then leave it in the rain and it’s 3.5

Dunno about the magic shrinking fabric (polyester iirc), but typical Aussie weirdness like 6′ by 4′ trailer beds, tarps to fit said trailers in Imperial while tarps to fit other stuff would be metric. And structural steel to fit the trailer would be metric, while the sheet for the bed is STILL available in Imperial.
OZ has been “Metric” since late ’60s/early ’70s

Having been raised in the 1970s and 80s in the US, I was thoroughly taught both units and can convert between them readily. This has been handy when talking to a close friend of mine who moved here from Canada, as I can convert most units from imperial to SI, which is all he was taught there.
Seems to me that both systems work just fine. Also, they were both based on arbitrary and changeable things (but have since come closer to being defined in terms of absolutes), so to say one is better than the other is like saying that one of your thumbs is better than the other. It’s just makes no sense.

They are rare enough in the US that you could probably get that much for it. I bought a ’97 passat in 2005 or so. The 1.9l diesel was twice the price for a car with twice the miles on it as the gasoline (VR6) version! It seems that most Americans who appreciate an economical car don’t want to pay for a new car, making the supply of used economical cars small.

unit (n) – Person who insists that their system of measurement is better and that you should switch to it regardless of differing price and availability of parts and tools using those units in your part of the world. Also, a person who insists that you use a system of measurement that differs from the one used in the fasteners and parts in your pre-existing, big-ticket and high-maintenance items such as your automobile.

Congrats to HaD for this trick to get a lot of comments to work again.
I assume it’ll boost financing and the life of HaD so us HaD readers benefit from it too so I don’t feel bad being ‘tricked’ into it too.Plus it was mentioned that it worked last time so we went in eyes open.

The only fail is that we don’t really achieve anything, it works on HaD, lots of comments, it works on Reddit, also lots of comments and attention, but neither cause any change really. Apart from perhaps reminding us to do an effort when we tend to slack, which if repeated enough might cause a very slow change in the world to use standards more comprehensively and make it a habit to include metric units when describing something in Imperial units.

I think it’s actually a bit odd that with things like big ‘global’ news organization they still can’t be bothered to type in the metric when using imperial in online new items, I guess what we need is to get the tools for submitting stories and posting articles to automatically add bracketed SI units behind imperial.

Idea:
So HaD staff, email those WordPress people and tell them to add that and make a difference today, because if it’s on WP at least many tech sites and bloggers will have the tool at hand.

And perhaps we should also get Google/Apple/MS/Mozilla to add it to input boxes! If that were a standard on browsers and android/iOS it would have quite an impact.
And how about a shortcut for HTML5 to indicate that a placed unit should have a converted SI unit placed behind it? Can’t be that hard to implement.

(with this second part of the comment I’ll be actually sad if Jenny removes it because I wrote it. But if she does I give permission to her to present it as her own idea or for other readers to do so.)

I have worked with both sets of units and I believe both have their place.

To the people who like metric units, remember that the base units are just as arbitrary as english units. A unit that is based on the distance light travels in 1 / 299,792,458 seconds might as well be a random number. At least I can pace out a foot, and I can do it surprisingly accurately, about 2% for 100ish foot spans.

The link to light of the meter was done later, originally it was based on the circumference of earth (one ten-millionth of the distance from the equator to the North Pole), but since that is not practical (nor precise) they used a standard meter rod, but since that’s not up to modern times they first used a certain number of wavelengths of a certain emission line of krypton-86, then since 1983 the meter has become based on a true fixed unit we believe, the speed of light.
So it’s not a random division really.

Also you can learn to hold your hands near a meter apart, or also pace it since your mentioned 100 feet is 30.48 meters. so you should be able to get close to 30 meters too with equal precision, just subtract one foot during your pacing and end up with 99 feet = 30.175 meter.
Not that I assume your feet (or shoes rather) are the exact size of the standard feet, such a coincidence would be quite unlikely.

I know about the lineage of most of the units that I use. But the fact is that english units are a lot more human friendly for things on single humans scale. As for my shoes, standard size 10.5 Keen Wellingtons. I have never measured them and I don’t walk exactly heel to toe.

“originally it was based on the circumference of earth (one ten-millionth of the distance from the equator to the North Pole)”

It was *targeted* to be that. It was never *defined* that way, because in the late 1700s no one had ever *been* to the North Pole, much less measured a distance that far. But they were able to measure shorter distances, and were able to measure how much of a shift in angle stars were staying along the same meridian. Unfortunately measuring that shorter distance proved to be a minor nightmare, imprisoning several and killing one of the surveyors. Their measurement was adopted, a standard meter was created (out of some high-purity bar of metal), and even after they found out later that their measurement was too short, no one wanted to resurvey things again and so they just kept the “too short” definition of the meter based on that bar.

The entire point wasn’t that the units were “better.” It was that it was possible to reconstruct a primary standard from a description of a measurement, *not* from an arbitrary standard. Hence the original meridional idea – anyone could go out and measure a distance along that meridian, and measure the angle change of the stars to figure out what portion of the meridian was just measured. Unfortunately it was a bit ahead of its time: it wasn’t until the 1900s that fundamental measurements like this became accurate enough to become the primary standards, which left us with slightly-quirky values rather than nice round numbers.

I find it delightful that people who argue unit systems tend to ignore the metric system’s primary virtue: easier conversion between measurable properties.

The difference between gasoline measured in liters and gasoline measured in gallons is precisely bupkis (AeEe|e<'I don't care'). The terms of any such argument can be applied without modification to an argument about measuring in liters versus milliliters. All such units have the same functional meaning, namely 'some', or more often, 'enough to fill the gas tank'.

The reason to measure the volume of gasoline at all is to perform a quantity-to-currency conversion. I invite anyone who wants to pick up the argument to explain how either the metric or imperial systems make it easier to do the following comparisons:

– 1L of gasoline in British Pounds at the outskirts of London -vs- 1L of gasoline in Japanese Yen at the outskirts of Tokyo.

– 1gal of gasoline in $USD at the outskirts of New York City to 1gal of gasoline in $CAN at the outskirts of Seattle.

For bonus points, calculate the radius of a copper sphere that contains 1 Coulomb of free electrons, assuming one free electron per atom, in centimeters and in inches. Yes, molar mass is defined in grams. Show your math to demonstrate how the additional calculation makes the Imperial version 'harder'.

The price of gasoline is pretty much floating randomly. So of course it’s just as easy/hard when comparing. And in fact the price of gasoline even when we all used the same coinage varies wildly from region to region, hell even from gas-station to gas-station there can be variation.
Talk about spiking the cards by picking such an example.

And it’s not true that “the reason to measure the volume of gasoline at all is to perform a quantity-to-currency conversion”.
We also measure it to determine how far we can travel with it and how much fits in a tank.
.
Also it’s amusing your second ‘test’ uses the SI unit Coulomb which itself is based on 2 more SI units. Perhaps you would be happier with a standard not based on ampere per second but on 2.54 ampere per seconds? Or some other more fractional value.

It is perhaps more amusing to recognize that Imperial/Customary are too obsolete to have noticed the invention of electricity, and have no electrical units of their own. They had to settle for “borrowing” the SI units.

We defined a set of things which actually had a good reason to stay Imperial (eg. nuts which had to fit imperial bolts installed in things), and over a period of about a decade sanctioned the rest. We didn’t embarrassingly neglect to update our street signage (looking at you, UK), and we didn’t set NIST to plan a conversion then do nothing more (that one would be you, USA). We did it over a time, with a transition plan, and very successfully. We didn’t listen to morons with grey hair who saw this as a political issue. This was basic common sense.

Almost nobody, even the oldies, uses miles anymore. Gallons: completely gone. Fahrenheit: what the frig do you holdovers like about this illogical and ridiculous temperature system? (Don’t bother answering: we’ve heard it. Self-justifying garbage. Water freezes at 0 and boils at 100. Below 10 is really cold, to 10-20 is chilly, 20-30 is nice, 30-40 is hot, 40-50 is sweltering, 50-60 is edge of life, and it hurts over 60. Convenient, nicely delineated.) Pounds?

There are still some weird vestiges of Imperial, though. Flat screen TVs are still measured in inches. People sometimes still give their height in feet and inches. Babies in pounds, but increasingly rarely, 19″ racks. Even these are dying.

The other interesting thing is because metric uses the same base as our numbering system, there is almost no need for fractions in measurement anymore. What an innovation, Imperial lovers, and please don’t give me crap about 12 dividing equally with 2,3 and 4, once we settled on a base 10 numbering system that ship sailed. We don’t need 1/2 a mile: we have 800m. And 500m. And 200m.

When I worked for Silicon Graphics, we released a brand new system whose installation manual was entirely in Imperial (even though most components in it were specified in metric sizes). I was ropable, and logged a documentation bug. The excuse which came back from tech docs was pathetic: “we don’t know metric measurements, we don’t know which one to select. Is it millimeters, centimeters, or meters for distances? Which do we choose? We don’t know.”

Morons. In metric, it doesn’t matter: you just move the decimal point.

When I was a teacher, any student who submitted an assignment with Imperial Measurements got an automatic fail.

HD’s are also in inch, but the M.2 SSD use metric though, both for connector pitch and sizes, so the Aussies can avoid damn inch there too :)
Plus PCIe also uses metric 1mm pitch, but no such luck on SATA though.

Shame some company somewhere managed to force an aspect ratio of 16:9 for laptops and thus any older (emulated or natively running) applications requiring low resolutions suffer from significant pixel stretch unevenness. That is some pixels are stretched as others are merged when scaling from the usual 16:10 or 4:3.
Oh and 4:3 scales better to 16:10 than it does to 16:9…
Also the menu bars obstruct the video when called into view on a 16:9 and are out of the way on a 16:10.
The UK government and the European Union should of put a ban on 16:9 laptop and monitor imports unless sold as a HD TV and banned from not having an OS that is a locked down TV viewing only OS.

I’ll include in the rant about those sideways screens in tablet PCs…. There should be a law that all tablet PCs with such sideways screens (9:16 ratio as opposed to 16:9 for example) have to have dialing capabilities and is banned from the title “Tablet PC” or restricted to the term “Phone”/”Phat Phone” or something.

Found via multiple Google searches I found there were and still probably loads of complaints from people who couldn’t find a 16:10 screen laptop roughly around the year 2011 onwards.

So reword your statement to:

“WE don’t like something so OUR governmentS should make a lawS that nobody else can have it either! FORCE SAID COMPANIES TO USE THE SANE SIZES and require the customer to place a taxable special order for the stupid peasant resolution and dimension screen”

It’s interesting, the whole miles on road signs thing. I was too young to know when they switched to metric, but I am guessing it was on a cost basis. The UK may not be a large country, but it’s densely packed and has a hell of a lot of road signs. Maybe Australia has proportionally less signage?

Things might have been different had miles been counted in base 12 or 16, but I am guessing that their use as a customary unit for travel doesn’t really impinge on any other areas.

Meanwhile all our Ordnance Survey mapping has been on a metric grid since decades before metrication. OS one inch to the mile maps – printed until about 1970 – have a 1km grid, for example.

Nope, no excuse there. Australia has more road signs per tax payer to pay for them but still changed them. New Zealand did it the same way as Australia where the cost was even worse as even more signs per tax payer. Sometimes you just have to suck it and make changes. We did it in the 70’s too. My prediction is UK will complete the process in 20 to 30 years and USA never because, well, its America.

I noticed that all that recent US storm coverage used miles per hour, but my weather reports either use Beaufort (an old unit from a British admiral going from 0 to 12) or meter per second, but not kilometer per hour.
And I think the BBC actually uses words like ‘gale force’ sometimes rather than a number.
So even there standardization is missing somewhat.

The National Hurricane Center and the National Weather Service officially measure in knots, and use that for marine and aviation products. They convert to miles per hour and kilometers per hour in products for the general public, but the media hates the metric system and usually drops the kilometers per hour.

Here, a few sailors might understand Beaufort numbers, but likely no one else. However, they are preserved in the wind limits for gale, storm, and hurricane warnings.

International METAR allows three suffixes to the wind field KT, MPS, and KMH (a suffix is ALWAYS required; there is no default for this field.). Usually each nation uses one and only one, KMH is fairly rare.

Well…. as I look UP at all the comments… it must be said that yet still I see only the same that I’ve seen since this question of olde came up. Argument… and some ridicule which is appropriately due because of the long long delay getting on board with metric, and I’m getting very tired of having to lug around DOUBLE the tools.

I used to say; “We are educated and organized, but not yet civilized.” I’ll have to drop the organized.

Only Double?
I assume AF and Metric…
What about Whitworth, both BSF and BSW, those weird sizes used for some plumbing fittings and the eentsie ones used for some auto electrical work??
Not to mention the lunacy with Hex, Torx – 5 and 6 pt, and security – which don’t seem to have ANY standard…
Tapered square peg drive, anyone – they can vary from the same BOX, never mind batch.
(sigh)

Drop the educated bit as well…. Maybe not for around here but in general.
I’ve seen enough dumb idiots to know the ratio of cognitive people (who think) to idiots is around the 1 to 20K by personal encounters, probably higher over a larger scale of the Anglosphere population.
It seems intelligence goes down when the necessary need for knowledge goes down…

Things that seem extremely important to the average pleb is as follows:

trap music (or demonic reggae… see Tommy Lee Sparta), soaps, Radio 1 music, Millennial-hipsters*, drama (including drama queens), Over obsession with celebrities for the sake of: “hey look at her tits!” and “Hey I wish I could be laid by him” type comments, He-said she-said, drama and more drama.

* Heck I didn’t even think this existed, yet this word is what it got auto-corrected to!

Well, it wasn’t *defined* that way at all. That’s just what they shot for. It was defined as the length of some random bar they had that they constructed based on a survey of the distances between two castles in France and Spain.

It’s not like they could actually survey the distance from the Equator to the North Pole in the 1790s.

The US pound is defined by the Kilogram. :) Whilst I’ve never read details of the famous space blooper, surely this can have nothing to do with the relative merits of unit systems, but rather exposed a hole in the systems integration testing and simulations prior to launch.

FFS. “We got hundreds of comments the last few times we dragged out Metric vs Imperial, I get paid according to some warped viewer-engagement measurement, and I have absolutely fuck-all of a better idea to write about. So everyone get ready for fun!”.

I can’t be bothered digging out the arguments I used last time. Just assume I think the same thing. I don’t need to post them, as everyone has already formed their opinion, and nobody’s going to change their mind based on anything anyone else says.

BTW I was expecting perhaps a post on some novel method of expressing things where units weren’t needed, somehow. Some universal system. Don’t know how it would’ve worked, and it’s probably impossible, but that’s what I had in mind when I chose to read this article. Not this disappointment.

Swatch also tried it, sorta:
“Swatch Internet Time (or beat time) is a decimal time concept introduced in 1998 by the Swatch corporation as part of their marketing campaign for their line of “Beat” watches.

Instead of hours and minutes, the mean solar day is divided into 1000 parts called “.beats”. Each .beat is equal to one decimal minute in the French Revolutionary decimal time system and lasts 1 minute and 26.4 seconds (86.4 seconds) in standard time. Times are notated as a 3-digit number out of 1000 after midnight”

“The concept was touted as an alternative, decimal measure of time. One of the supposed goals was to simplify the way people in different time zones communicate about time, mostly by eliminating time zones altogether”

That last bit makes some sense these days, now everybody and his granny is constantly online and many people communicate globally. Although some people who use internet a lot still seem to only talk to a narrow regional group or locals, even if they speak English.

Well the really annoying thing is dates, why does the rest of the world have to suffer the stupid choices of the US to use Month Day Year, this is totality illogical. Every bit of software defaults to Month Day Year, you cant sort, there is no progression, and if the Month is in digits there is confusion as to what the date is.

The answer is to use a logical progression Year, Month, Day, and if that is followed by the time Hour, Minute Second and it easily sorts, and is a logical progression.

As for sorting, computers use an internal format and sort correctly regardless of your display setting AFAIK. although that doesn’t apply to text files of course.
And talking of settings, computers, and probably phones too, have an option to set your preferred/regional format and you can set it to YYYY-MM-DD if your wish. you can also select if you want the comma or period as 1000 separator vs fraction one.
Which is another oddity, in Europe countries use the period where the US uses comma in numbers, and vice versa. Which is annoying since the keypad on keyboards have a period so you can’t easily use the keypad unless you reassign the period key on said keypad, but then other programs get confused.

YYYY-MM-DD is ideal. In the US, we push the year off to the end MM-DD, YYYY. The rest of the world just reverses the ideal completely. As far as I’m concerned, its an issue similar to coding styles. As long as it not a bad coding style that makes things much more difficult to maintain, just standardize and get used to it.

One minor edit.. the missed conversion wasn’t from Imperial units it was from US Customary units. The 2 systems are very similar, and US customary is derived from the Imperial system, but they are not the same. The sizes of the units and the reference points they use have changed seperately over time.

That is technically true, but only some units are different. For the particular units in characterizing a thruster, there is no difference. But when the data is supposed to be in newton-seconds, and you supply poundforce-seconds, there is a difference, and the probe was behind Mars, unobservable, and executing a string of orbital insertion burns. Had NASA characterized the thrusters themselves, they likely would have followed the terms of the contract but they outsourced to a supplier who didn’t.

It’s easy to say that without understanding historical context. Moving decimal places around is completely natural to us today and has been for a couple hundred years. Before that fractions were the name of the game. Many of the units have origins when the zero was not in common use in Europe. Feet divide easily into halves, thirds, fourths, and sixths. The weird thing about the mile though, it was originally 5,000 feet, but then the definition of the foot changed and rather have all the surveying data be wrong they changed the definition of the mile. Dumb, yes. Other units generally follow how numbers were dealt with, smaller groups combining into bigger groups.

But really, if everyone would just switch to a base 12 or base 60 system like the Babylonians originally intended, we probably wouldn’t be having this discussion. BTW, the words ounce and inch literally mean 1/12th. Different competing ounces later subdivided this differently, 10, 15, or 16. We still use the old system of subdivision for time as it’s so nice to be able to easily divide days, hours, and minutes into halves, thirds, fourths, sixths, etc.

Tyre diameter in inches but width in mm
35 and 16mm film length measured in feet

My dad imported some American Walnut to make a bench for me, it was sold in cubes (yards, feet?), then planed down into certain mm thickness planks but those mm were based on traditional fractions of inches thickness for wood. Carpenters still seem to like mixing units. After all we all still know what 2 by 4 plank is – it’s fairly self explanatory.

As an engineer, I’ve submitted to the fact that at least 10% of my job will always be unit conversion and unit checking. This is so much a fact of life that during my orientation, a fellow engineer turned department director quizzed me on the conversion factor between kW and HP.

I am an engineer who despises the metric system.
It is French and it shows: the units are either too large or too small in daily use and the dozenal system was used
thanks to it’s utility in daily use.
Frankly I see the Metric System as part of the dumbing down on the masses and it brings everyone down to the level of the French and darkies.
Fight for your right to use your TRADITIONAL UNITS, PEOPLE!

I am from neither of the groups you despise so, but I am also an engineer. I gather you are one of those engineers who do no engineering calculations, as doing them in an irrational, incoherent system is a complete nightmare. SI for the win. I like measurement systems in which force really is equal to mass times acceleration without hokey made-up units like slugs or poundals> my calculator doesn’t do dozenal and I like being precise.

Knots and nautical miles have a direct relation to the roughly spherical shape of Earth, which is exactly why they prevailed in nautical and aerial navigation (with the exception of ultra-light aircraft in Europe). Unfortunately, that’s also the reason the connection between distance, speed, and position on the surface only works on Earth.

Really, when you use spherical trigonometry, you get answers in degrees of arc. Whether you multiply by 60 nautical miles per degree or 111 km/degree makes little difference, and you are still only accurate to around 1/2% as the earth is more nearly an ellipsoid, for which Vincenty’s equations must be used.